50 setxunit
7.5 setborder
90 setangle_repere
-5 5 setxrange
-1 5 setyrange
1 1 settkstep
.5 .5 setsubtkstep
2 2 setmkstep
ticks
subticks
marks
traceaxes
axesarrow
.75 setlinewidth
continu
bleu
/X {settvar
#rpn#   (1+Tan(t/2))*Cos(t)
} def
/Y {settvar
#rpn#   (1+Tan(t/2))*Sin(t)
} def
  0.00001  20 {X} {Y} Courbeparam